Normally a request contains one or more request objects, and once all objects are marked as 'completed' the request itself is completed and userspace gets a signal that the request is complete. Calling vb2_buffer_done will complete a buffer object, and v4l2_ctrl_request_complete will complete a control handler object. In some cases (e.g. VP9 codecs) there is only a buffer object, so as soon as the buffer is marked done, the request is marked as completed. But in the case of mediatek, while the buffer is done (i.e. the data is consumed by the hardware), the request isn't completed yet as the data is still being processed. Once the data is fully processed, the driver wants to call v4l2_ctrl_request_complete() which will either update an existing control handler object, or add a new control handler object to the request containing the latest control values. But since the request is already completed, calling v4l2_ctrl_request_complete() will fail. One option is to simply postpone calling vb2_buffer_done() and do it after the call to v4l2_ctrl_request_complete(). However, in some use-cases (e.g. secure memory) the number of available buffers is very limited and you really want to return a buffer as soon as possible. In that case you want to postpone request completion until you know the request is really ready. Originally I thought the best way would be to make a dummy request object, but that turned out to be overly complicated. So instead I just add a bool manual_completion, which you set to true in req_queue, and you call media_request_manual_complete() when you know the request is complete. That was a lot less complicated. The first patch adds this new manual completion code, the second patch adds this to vicodec so it is included in regression testing, and the last patch is an updated old patch of mine that adds debugfs code to check if all requests and request objects are properly freed. Without it it is really hard to verify that there are no dangling requests or objects. I prefer to merge this third patch as well, but if there are objections, then I can live without it. Regards, Hans Changes since v2: - fixed use-after-free bug in the third patch in media_request_object_release(). Changes since the RFC: - Added WARN_ONs - vicodec was calling media_request_manual_complete() without checking that it was the stateless output queue first. - Some minor cleanups in patch 3. Hans Verkuil (3): media: mc: add manual request completion media: vicodec: add support for manual completion media: mc: add debugfs node to keep track of requests drivers/media/mc/mc-device.c | 30 +++++++++++++ drivers/media/mc/mc-devnode.c | 5 +++ drivers/media/mc/mc-request.c | 44 ++++++++++++++++++- .../media/test-drivers/vicodec/vicodec-core.c | 21 +++++++-- include/media/media-device.h | 9 ++++ include/media/media-devnode.h | 4 ++ include/media/media-request.h | 38 +++++++++++++++- 7 files changed, 144 insertions(+), 7 deletions(-) -- 2.43.0
